Sleep and sleep disorders

Sleep is a normal state of decreased consciousness and lowered metabolism
during which the body rests. As a natural, necessary, and daily experience
for humans and most other vertebrates (animals that have a backbone or
spinal column), sleep has four stages through which we cycle several times
a night. A sleep disorder is any condition that interferes with our
regular sleep cycle, ranging from insomnia (pronounced in-SAHM-nee-a) to
narcolepsy (pronounced NAHR-ko-lehp-see).

Necessity of sleep

Although sleep is something everyone experiences everyday—the
average person sleeps approximately one-third of his or her
lifetime—science still has a great deal to learn about this very
common phenomenon. We all recognize that sleep is a necessity and that
although we can go without it for a while, it eventually becomes as
important to our health and well-being as food, air, and water. We also
know that when we sleep well, we seem to wake refreshed and alert, and
generally feel ready to face the day. When we do not sleep well, however,
we know that the chances are greater that we will feel less sharp and
probably more grumpy than usual, and that everything may be a little more
difficult to do. People who regularly experience a problem falling asleep
or staying asleep may be suffering from some form of sleep disorder.
Serious sleep disorders can wreck our personal lives, make us unproductive
at work, and overall, injure the quality of our lives.

Purpose of sleep

The real nature and purpose of sleep has long puzzled scientists. Ancient
humans believed that the soul left the body during sleep, and the
well-known prayer that includes the words, "if I should die before
I wake," tells us something about the fear we may experience when
we surrender to unconsciousness every night. From a scientific standpoint,
sleep was not able to be studied seriously until the twentieth century
when certain instruments were invented that could actually measure brain
activity. In 1929, the German psychiatrist Hans Berger (1873–1941)
developed a machine called an electroencephalograph (pronounced
ee-lek-troen-SEH-fuh-low-graf), which could pick up and record the signals
produced by the brain's electrical activity. By the mid-1930s,
Berger was producing a graphic picture or photograph of people's
brain waves, both waking and asleep, that was called an EEG or
electroencephalogram
(pronounced ee-lek-tro-en-SEH-fuh-low-gram). An EEG is made by placing
electrode wires on a person's scalp that receive the electrical
activity produced by the brain's neurons or nerve cells. Neurons in
the brain receive and transmit information and are able to communicate
with the rest of the body. When they are "firing" or
activated, charged electrical particles are produced. It is these charges
that the EEG can sense and record.

Words to Know

Apnea:
Cessation of breathing.

Circadian rhythm:
The behavior of animals when influenced by the 24-hour day/night cycle.

REM sleep:
The period of sleep during which eyes move rapidly behind closed
eyelids and when dreams most commonly occur.

Stages of human sleep

Scientists who study the brain have discovered that certain types and
levels of brain activity have their own typical patterns or register their
own type of waves on an EEG. They also have come to recognize and name the
certain types of waves that relate to certain types of activity. For
example, when a person first closes his or her eyes after lying down,
"theta" waves, or waves that have a certain number of cycles
per second, are produced. As a person falls into deeper stages of sleep,
the waves become slower. Although they do not know exactly why this
happens, scientists do know that most vertebrates pass through two
distinct types of sleep, and that humans have four separate levels of
sleep. In Stage I we have just fallen asleep, usually after about fifteen
minutes, and we have entered a light, dozing sleep. Here we show irregular
and fairly fast theta waves. Stage II is the first true stage of sleep,
and our EEG registers "spindle waves" in bursts. Stage III
marks the beginning of deep sleep, and
theta waves that are slowed-down appear. Stage IV is our deepest sleep
and has the slowest waves of all, sometimes called delta waves. This
progression from stages one to four takes about one hour, and then the
cycle reverses itself, going backwards to Stage I. This entire cycle
repeats itself three or four times during the night.

REM sleep

At the end of the first cycle, each time a person reenters Stage I, he or
she begins an interesting sleep stage called Rapid Eye Movement or REM
sleep. It is during this stage that our dreaming occurs, and even though
this is a stage of light sleep, most people are difficult to awaken when
in REM sleep. Our bodies are also very active during REM, and besides our
eyes moving side to side, we usually toss and turn quite a bit. of sleep a
night. Most adults average around seven and a half hours of sleep a night,
although studies have shown that some people need as little as five or six
hours. Regardless, everyone needs their REM sleep. We spend about
three-fourths of a night in non-REM sleep and one-fourth dreaming in REM
sleep. Amazingly, the brain waves registered during REM are almost the
same as those when we are awake.

How much sleep?

Our sleep patterns change as we age, and infants sleep far longer and
deeper than adults. Newborns may sleep as much as seventeen hours a day,
while five-year-olds about twelve hours a night. Teenagers need about nine
and a half hours a night, although they seldom get that much. For some
reason, many people experience the best and most satisfying sleep of their
lives during the middle teen years. Some very old adults need only five or
six hours a night.

Insomnia

Although sleep is something that is common to us all, many
people—as many as 30 million Americans—suffer from some sort
of sleep disorder or problem. Insomnia or difficulty falling or staying
asleep is the most common disorder. While everyone will experience this at
some time, if you regularly have trouble getting to sleep or staying
asleep and feel next-day sleepiness and difficulty concentrating, you
probably have insomnia. Some of the causes of insomnia are psychological
factors like stress. Your lifestyle itself may cause a different kind of
stress if you regularly work or party very late or drink alcohol or
beverages with caffeine. An unsettling environment can be a factor, as can
physical
problems that cause pain. Certain medications can also cause sleeping
problems. A simple description of insomnia is that it happens when the
part of the brain used for thinking does not turn off.

Narcolepsy

Probably the most serious sleeping disorder is a chronic brain disorder
called narcolepsy (pronounced nar-ka-LEP-see). It affects some 200,000
Americans and is recognized primarily by a sudden, almost uncontrollable
need to sleep that can occur at any time. Narcoleptics may also experience
sudden muscle weakness, a feeling of being paralyzed, and even especially
frightening nightmares and hallucinations. It can be brought on by being
bored but also by being surprised, angry, or suddenly upset. The poor
narcoleptic always feels tired during the day. This difficult condition is
a genetic disorder, meaning that it runs in families. It is managed with
stimulant-type drugs.

Many hospitals and universities run sleep labs where they monitor the
sleeping patterns of people with varying sleep disorders.
(Reproduced by permission of

Photo Researchers, Inc.

)

Sleep apnea

Sleep apnea (pronounced AP-knee-ah) sounds like a funny condition when it
is described, except it can be potentially very serious. Sufferers from
sleep apnea can develop high blood pressure and even risk heart damage.
This condition occurs most often in middle-aged men who literally stop
breathing while asleep. When this happens, they usually snort or snore and
gasp for breath, waking themselves up. This can happen as often as two
hundred times a night, obviously wrecking any chance of a good
night's sleep and leading to daytime sleepiness, headaches,
irritability, and even learning and memory problems. Most cases are caused
by some sort of abnormality in the nose, throat, or other part of the
airway. Some sufferers can wear a masklike device over their nose whose
regulated pressure prevents their throat from collapsing during sleep.
Others may need surgery.

Other sleep disorders

There are several other types of sleep disorders, some serious and some
simply bothersome. Some people have Restless Leg Syndrome (RLS), in which
they experience terribly uncomfortable sensations in their legs and have
to move, stretch, or rub their legs all the time. This naturally disturbs
their sleep. This condition is sometimes treated with drugs. Others have
Periodic Limb Movement (PLM), in which their legs (and sometimes their
arms) periodically twitch and jerk, sometimes for as long as several
hours. Like RLS, the cause is unknown.

Many people who work or are active during the night and try to sleep
during the day experience difficulty sleeping. This is called a disruption
of one's circadian (pronounced sir-KAY-dee-an) rhythm. This means
that the body's internal clock is out of sync with the
twenty-four-hour day. The "jet lag" we feel after changing
time zones is a temporary example of such a disorder. Finally, many people
at some time have experienced other minor disorders, such as sleepwalking,
"night terrors," teeth grinding, and talking in one's
sleep.

Although scientists are still not sure exactly what the function of sleep
is—whether the brain is "housekeeping" and
reorganizing the information it took in during the day or simply
conserving its energy—they do know that it provides all-important
rest to the mind and body, and that rest is essential to good health.
Therefore, sleep is not simply a "time out" from business.
It is a necessary time of restoration. This is demonstrated by the ill
effects experienced by those who suffer from a sleep disorder.

User Contributions:

i wanna know if there are different types of sleep. i take forever to fall asleep but i stay asleep and barely move for a reallllly long time. my boyfriend falls asleep so fast but wakes up easlily and toses and turns all night.. is there types or does it just depend on the person

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